The objective of this R03 application is to demonstrate quantifiable spatiotemporal differences in macroscopic electrical activity of human sensorimotor cortices during voluntary isometric torque generation in the upper limb. Using a combination of high-resolution EEG measures, a novel quantification technique and a 6 degree of freedom load cell controlled isometric paradigm, it is proposed to quantify differences in spatiotemporal electrical brain activity during the generation of static torques in different directions and of different magnitudes. Specifically, it is postulated that the magnitude (intensity) of electrical brain activity scales monotonically as a function of load magnitude (Aim 1). Furthermore, it is postulated that the spatial organization of cortical activity, expressed in terms of an area of activation and its center, is a function of load direction and not a function of load magnitude (Aim 2). Cortical locations identified by the EEG measures will be verified using event-related fMRI (Aim 3). The preliminary results indicate the presence of a clear monotonic relationship between the magnitude of cortical activity and the magnitude of joint torque generation (Aim 1). Preliminary findings also demonstrate a strong spatiotemporal correlation between the location of centers of electrical brain activity and elbow/shoulder static joint torque direction (Aim 2). Specifically, pilot data demonstrates that the approach has the ability to separate joint torque direction at a single joint. For example, one is able to distinguish, for the first time, quantifiable differences between the location of cortical activity associated with elbow flexion and elbow extension as well as shoulder abduction and shoulder adduction torques. This investigation will expand the study of cortical activity as a function of joint torque direction by increasing the number of torque directions generated at the elbow and shoulder joints from four to eight directions. The characterization of spatiotemporal electrical brain activity proposed in this study is likely to lead to future research on cortical organization which will seek to distinguish joint torque from muscle activation based encoding schemes. Furthermore, quantification of spatiotemporal electrical brain activity in healthy human subjects provides the backdrop for similar studies in stroke subjects, which will examine the cortical substrates underlying the known impairments of available muscle and torque combinations in this population. Taken as a whole, the proposed study may substantially enhance our understanding of motor cortical activity in the healthy human brain and provide foundations for further scientific inquiry into mechanisms of cortical reorganization following hemiparetic stroke, which may lead to the development of more effective neuro-therapeutic interventions.